Wireless communication systems may comprise cellular systems, such as global system for mobile communication, GSM, wideband code division multiple access, WCDMA, or long term evolution, LTE, systems. Wireless communication systems may also comprise non-cellular systems, such as wireless local area network, WLAN, or worldwide interoperability for microwave access, WiMAX, systems.
A wireless terminal, such as for example a smartphone or tablet device, may be furnished with capability to attach to more than one type of system, for example a wireless terminal may attach to GSM and WLAN systems. When both types of system are available, the wireless terminal may decide based on various rules, which type of system to use for communication.
A cellular system may comprise large-area cells, or macrocells, to achieve large-area coverage. A cellular system may comprise small cells, which may be referred to as hotspots, microcells, picocells or femtocells, for example. Small cells may be disposed inside cell coverage areas of macrocells, for example to provide increased communication capacity in areas of high traffic. Small cells may be configured to provide high datarates for data-intensive usage. Small cells may operate using cellular or non-cellular technology, and they may be independent of a wide-area cellular system or comprised in a wide-area cellular system as local hotspots.
Where a small cell resides in a cell coverage area of a macrocell and the small cell is comprised in the same overall system as the macro cell, the system may prefer to offload at least some traffic from the macrocell to the small cell disposed inside the macrocell. This may be achieved by handing over mobiles from the macrocell to the small cell. After such a handover, the mobiles may communicate with the base station or access point controlling the small cell, rather than with the base station controlling the macrocell.
Offloading to small cells may be especially useful in case the small cell operates on a different frequency than a macrocell surrounding it. When the frequency is different, radio communication between a mobile and the base station or access point controlling the small cell cannot cause interference to communications between mobiles and a base station controlling the macrocell. On the other hand, it is more difficult for a mobile to find a small cell operating on a different frequency than a macrocell surrounding the small cell, while the mobile is attached to the macrocell.